This invention relates to a solar cell and to a method for making a solar cell.
In particular the invention relates to a solar cell with a semiconducting doped substrate that has a first surface, a second surface opposite the first surface, and an edge surface. An emitter layer is applied to the first surface and a number of recesses are filled with metal to form electrical conductors. The electrical conductors are contacted by a first electrode, and a metal layer is applied to the second surface as the second electrode.
U.S. Pat. No. 4,726,850 discloses a method for producing a solar cell and a solar cell with so-called “buried contacts.” “Buried contacts” ordinarily means electrical conductors designed as deepened or entrenched contacts that are introduced in recesses of a first surface of a solar cell. The depth of the recesses is considerably greater than their width. Solar cells designed in accordance with this patent are usually contacted on the first surface and on a second surface located opposite the first surface. This arrangement has the drawback that in a modular circuit of a plurality of such solar cells, electrical connections have to be made between the first surface and the second surface. This arrangement is not only relatively costly to produce, but also holds considerable risks of malfunction because of damage to the electrical connections of the solar cell wiring.
U.S. Pat. No. 4,361,950 discloses a solar cell with an arrangement of conductors wherein a conductor grid is applied to a first surface. The conductor system according to this patent also has contact sections that extend from the conductor grid around an edge face of the solar cell to a second surface opposite the first surface, and which serve as an n-electrode. After costly masking and abrasive treatment to remove n-conducting layers, a metal layer serving as a p-electrode is made on the second surface in the edge region. In this solar cell, it is indeed possible for the second surface laid on the back face to make contact with the two electrodes with proper arrangement of the solar cell. This, of course, has the drawback that the conducting grid may significantly reduce the efficiency of the solar cell because of the not inconsiderable shadowing of the first surface.
The task underlying the invention is to provide an efficient method for producing a solar cell, especially with deepened or entrenched contacts, so-called “buried contacts,” which contact on the back face of the solar cell.
The invention is also based on the task of describing a solar cell of the aforementioned type with contacts on the back face.